The present disclosure generally relates to semiconductor devices, and particularly to a semiconductor structure having a gate dielectric comprising a stratified gate dielectric stack comprising two atomic interfaces that provide discontinuities in the band gap structure of the gate dielectric, and methods of manufacturing the same.
One of the main challenges in advanced high-performance field effect transistors is the high gate leakage current through a high-k gate dielectric between the gate electrode and the body of a field effect transistor. The high-k gate dielectric consisting of a single homogeneous dielectric material requires to be continually reduced in thickness to obtain higher performance of the field effect transistor but at the expense of increased gate leakage.
Addition of a capping layer over a high-k dielectric has been known to result in simultaneous modulation of the work function of the gate stack. In prior art gate stacks including a capping layer, the material of the capping layer inter-diffuses into an underlying high-k gate dielectric and an interfacial layer there below. Further, the material of the capping layer also diffuse into a work function metal in the gate electrode.